Manufacture of cellulose articles from viscose



July 11, 1950 J. A. CALHOUN MANUFACTURE OF CELLULOSE ARTECLES FROM VISCOSE 2 Sheets-Sheet 1 Original Filed Aug. 14. 1946 INVENTOR. JOHN ALFRED CALHOUN ATTORNE July 11, 1950 A o N 2,514,471

' MANUFACTURE OF CELLULOSE ARTICLES FROM VISCOSE Original Fi led Axig. 14, 1946 2 Sheets-Sheet 2 1 I ['15 I T IF ENTOR. JOHN ALFRED CALHOUN ATTORNEY.

Patented July 11, 1950 UNI TED STATES PATENT OFFICE J ohwAlfred Galhoun ,.Swarthmor,e;. Pa-.;.. assignor;

-.t.o. Americant Viscose: Corporation, Wilmington, Del a. corporationof Delaware "Original application-August 14,- 1946, Serial No. 690,546. Divided and thisapplicationFebruary 26, 1949, Seria-LNo; 78,601

"7 Claims, .1

This invention relates to the manufactureoi cellulose. articles irom viscose.

.Th-is,-is, a-division. ofi myapplication Serial No- 690,546..filed- August. 1.4,19i6... now. Patent. No..

In accordance with common. practice. regenerated cellulose. articles. are: manufactured by. ex-

truding-...the -viscoseintoman acidsetting bath,.

usually comprising.anaqueoussolution of. sodium sulfa-te sulfuric acid, and. .zincpsulfate. or itsequivalent. .During-thespinning... or. casting; operations, theibatnisiouled. by impurities in. the. f ormof. dispersed particles resulting; from. decomposition of; the .viscosa-which-impurities gradually accumulate in the. bath.v and: remain suspended therein. Eventual1y,..the. .bathmusabe. discarded or treated in. some. manner to.. remove the..dis-- persed-particulate impurities tovavoid discoloration. and contamination of. .the.-.r.egenerated, cellulosevarticlessbeing. formedincthe. bath. --.Since large volumesof the batlra-re required, it .is -.usual,. for reasons o--economy,. to. withdraw thafouled bath. from the-spinning. tank or. other vessel, clarify. 'itrby. removal ofi-the. impurities! arising. from the viscosedecompositiom, condition it. for re-use. (as bythe removal. of. excess .sodium sulfatebuilt up therein, during the, spinning. operation and .lthe addition :of. sulfuricsacid. thereto). ,.-and. then return the ,bathlto, .the spinning-tank.

Theimpurities. or contaminants resultingufromp decomposition. of. .the. viscose occur inthe form. of extremely. finesolid particles comprisingsulfur and; sulfur compounds :including. higher. thionic acidslapparently. producedby reaction between. thesuliur. .dioxideand hydrogen sulfide. liberated during regeneration. of .-.the.lcell'ulose.asl well as. compounds. formed, by. reaction of thee thionic. acids withthe metal...commonly lead,..comprising the vessel. containingthe bath landin. which...the casting or. spinning operation is performed v Re mov'al of the solid suspendedimpuritiesvfromthe bath .to. .the -extent required to.. obtain .a bath of the necessaryshighsdegree. of. clarity .is greatly complicated; by theextremely. finely. divided con dition of .the impurities." in the. bath. Filters. of. ordinary type cannot beusedior. clarifyingthe bath. because the .particles are so .fine that they readily pass through the. filter .with-..the solution... Although the setting bath-.may be clarifiedsatisfactorily by, passing it -.thr.ough'j special .filters,.-

- 50 such as. charcoal filters, which absorb impurities from .a'cid; media. suchffilters. are. relatively expensive, and, furthermore, require, quitel frequent removal from service. for. back-washing.

stand in-a-settling tank or. the like until the impurities settle out. of suspension. and collect as sediment. at the bottom of. the tank, but the impurities are so fine and settle out so gradually under, ordinary conditions, that-the .timerequired to. obtain-a clarified bath ofthe .requisitehigh degree ofclarity is too-long torender. thatmethod of. clarification-feasible. for-use. in conjunction with. continuous processes. for. the.- manufacture of cellulose-articles. :from-yiscoseon. a commercial basis.

It is one. object-of.- this invention; to provide an improved method for the manufacturer-of cellulosic articlesfrom. viscose, by the wet spinning method, .in whichithe setting bath. is continuously clarified, conditioned-for reeuset and recirculated to the spinning orscasting vessel. .Another object is to provide.an,..imprcved. method ofclarifying contaminated. acid, setting-. baths? resulting from the-decomposition ofv viscoseto form regenerated cellulose articles.v .1 Another. object; is to. increase the rate at which. the .solidcontaminants present in such baths settle out. on.precipitateirom-the solution. A further object is. to provide an improved. 1 method. of. clarifying. the baths which is adaptable. touseJin. conjunction with and as a stage. in continuous spinning or; casting operations.

The. objects of the. invention. are accomplished of. the.high.-requency.sound .waveradiationathe: rate, of: settling out, of the-impurities, is greatly acceleratedand, usually, .the sedimentis produced and'the. desired clear. solution; is.-obtained. in-- a relatively shorttime, seconds-orminutes;-.as-comparedwithrthe. hour-s required-for-normal settling.

The. .high. frequency. sound. wave 1 radiationshave the effect. of aggregatingwthe. original particles, which are usually microscopic, into largeragg-ra gates which may beclarifiedamacroscopic; 1 Baths containingthe. aggregated particles may.- be: c1ari--" fied by .passing. .the. bath. through, conventional acid -proof filters. or. centrifuges which will retainthe aggregated impurities.

Thehigh frequency. soundwaveradiations. may

be generated. by. means of. any. suitable sound.- generating device. such a." suitably insulated It is possible, oi;coursettclpermiti the.bath. ..to,. 55p piezoelectric. sound. generator. a. magnetorstriction sound generator, or an electromagnetic sound generator. The waves may be propagated in the contaminated bath after it has been Withdrawn from the extrusion zone, and intermediate the tank and a reconditioning or regenerating system in which the relative proportions ofthe constituents of the bath are readjusted to condition it for re-use. Again, a sound wave irradiation zone may be established in the path of the bath as it flows through the spinning vessel or tank, beyond the point of extrusion of the viscose into the bath, and the bath may be passed at a controlled rate through the irradiation zone-as it flows toward the exit end of the vessel to effect rapid settling out of the suspended impurities present therein as a result of the viscose decomposition. The sediment thus produced at the bottom of the vessel or tank may be withdrawn without interrupting the spinning operation. Within the scope of the invention, the fouled bath may be simultaneously or successively subjected to irradiation by sound waves having difierent frequencies within the range stated, and of different magnitudes.

The spinning bath may be degassified in any known r appropriate manner, prior to propagating the sound waves therein, to prevent dissipation of the vibrational energy due to the presence of gas bubbles, such as bubbles of hydrogen sulfide gas, which may occur in the bath.

The accompanying drawing is illustrative of apparatus suitable for practicing the invention. In the drawing,

Figure 1 is an elevation view, partly in section of apparatus suitable for carrying out one embodiment of the invention;

Figure 2 is anelevation view, partly in section, of apparatus suitable for carrying out another embodiment of the invention.

Figure 3 is an elevation view, partly in section of another modification of the invention; and

Figure 4 is a side elevation, partly in section, of a still further modification.

Referring to Figure l, the viscose is continuously extruded through a spinneret 2 positioned in vessel 3 to extrude the viscose in a generally horizontal direction into the acid regenerating bath which is continuously introduced into the vessel, at a controlled constant rate of speed,

through pipe 4 to form'flbers of regenerated cellulose which are continuously withdrawn from the bath through a guide 3d. The bath in vessel 3 is maintained at a constant level, an overflow pipe 4a being provided for this purpose. The overflow is continuously withdrawn by the action of pump 5, and circulated through pipe 6 to a settling tank 1 having a cone-shaped bottom 8. A sound generator 9 is supported above the settling tank I and'has associated-with it a tube It] which projects'into the tank to transmit thevibrational energy to the bath entering the tank to effect rapid settling out of the dispersed particulate impurities. The impurities 'collect in the coneshaped bottom of the tank to produce a sediment which may be withdrawn either continuously or intermittently to a sludge collector or the like. The clarified supernatant liquid eventually overflows the tank and is circulated through pipe H, to a regenerating or reconditioning system l2, in whichitis conditioned for re-use, after which it is recirculated, by the action of pump I3, through pipe 4 to the spinning vessel 3. The rate at which the bath is delivered'to vessel'3, andthe rate at which the spent bath is withdrawn from the vessel and discharged to and from the settling 4 tank I is controlled to insure viscous non-turbulent flow of the bath through the sound wave field, so that the contaminated solution is exposed to the action of the waves for a time sufficient to permit deposition of the aggregated impurities. 1

Instead of continuously circulating the bath through a field of high frequency sound waves, the clarification may be efiected on a batch basis, that is, the spent bath may be withdrawn from the spinning vessel and stored for a predetermined period of time in a settler similar to tank 1 in which it is subjected to the high frequency sound wave radiations, to produce a sediment consisting of the dispersed particulate impurities, after which the clarified bath may be conditioned for re-use.

Figure 2 is illustrative of apparatus which may be used when it is desired to effect clarification of the bath while the bath is present in the spinning vessel.

As shown in Figure 2, the bottom of vessel 1 4, in which the spinning operation is performed, is

provided with a depression forming a trap l5, at

a point removed from the spinneret l6 positioned therein to spin the viscose in a generally horizontal direction into the setting bath. A pair of,

acid proof filters or screens [1 and I3 are fitted into grooves in the inner walls of vessel l4, so

that they extend across the vessel in inclined relation to the inner walls thereof, and on either side of trap IS. A sound generator I9 is secured in a bracket 20, mounted on the face of the spin ning machine above the level of vessel IA, and the 35 transmission tube 2| associated with the generator projects into the vessel, between the elements I! and i8 and above trap IE, to transmit the vibrational energy to the bath. The bath, which is continuously introduced into vessel 14 through .wave field. The impurities which accumulate in The clarified supernatant liquid passes through' screen la and is withdrawn from the vessel over overflow pipe 23, being forwarded to a regenerating or reconditioning system and recirculated to vessel H in the same manner asdescribed in connection with Figurel.

The arrangement shown in Figure 2 may be modifiedto provide a plurality of depressions or traps l5 at spaced points along the length of a conventional spinning vessel and beyond each of the spinnerets positioned therein, and a plurality of pairs of filters or screens l1 and 18 may be supported in the vessel in inclined relation to the walls thereof and on either side of each of the traps, to define a series of vibration or irradiation zones into which a transmission tube associated with a sound generator projects, to subject the contaminated bath to the high frequency sound waves at different points along. the path of viscous flow of the bath, through the vessel.

Instead'ofsprovidingzan irradiation'izonei bea yondeach of the individual spinnerets positioned if: in the spinning vessel; thedrradiatiorrszonescmayz: be" spaced along :the lengtir of the vesselz betweeni.

showny the spinnerets- 24mm positioned in'ivesselz 25' to-spin the viscose-generally verticallyi'upe;

wardly into the sspinning bath. lSL'ETCOIlJ-L tinuously "introduced at one: end of th 'vessel and withdrawn'; fat: a constant ac'o'ntrolledii rater: atthe opposite end; Thenbathflflows: .longitudiz-r show-hi, the weirs having slopedrsides im 'and' 29 defining traps in which the sediment pro- 1.-

duced' under vibrational action. of transmission tubes 36 and 3| associated wi-th, the sound generators 32 and 33 mounted in brackets 34 and 35 on the face of the machine is collected. Bafiie plates 36 and 3'! are supported on the vessel and project into the irradiation zone adjacent the tubes 30 and 3!. The baflie plates serve to deflect the bath downwardly and to retard the flow thereof through the vessel to afford ample opportunity for the impurities present in the bath to settle in the traps at the bottom of the vessel, from which the sediment may be withdrawn to a Waste disposal system. Irradiation zones defined by pairs of spaced weirs similar to weirs 26 and 21 into which the transmission tube associated with a sound generator projects, may be provided beyond a group of six spinnerets as shown, or beyond a group of spinnerets consisting of two spinnerets or more, or the irradiation zones may be provided beyond each individual spinneret, in the path of the flow of the bath from the inlet to the outlet end of the vessel, and may be provided at regular or irregular intervals along the length of the machine. That is, depending upon prevailing conditions, the acid setting bath may be passed into a sound wave irradiation zone as frequently as is necessary during the spinning operation to insure that the bath into which the viscose is extruded has the necessary high degree of clarity.

The arrangement for effecting clarification of the contaminated bath shown in Figure 4 is similar to that illustrated in Figure 3, but there the bath entering the spinning vessel through pipe 38 is forced over a weir 39 and then flows transversely of the vessel M1, and as shown, generally transversely of the direction of spinning, being withdrawn at the opposite end of the vessel through pipe 4!. Although only one irradiation zone is shown in Figure 4, defined by the weirs 42 and 43, and only one sound generator 44 having a transmission tube 45, and a single baffle plate 46 are shown in the drawing, it will be readily understood that a plurality of irradiation zones may be provided along the length of vessel 40 and that such zones may be provided beyond each of the spinnerets positioned in the vessel, or beyond a group of spinnerets comprising two or more spinnerets. In Figure 4, the spinneret is shown positioned to spin the viscose generally horizontally into the bath. However, it will be apparent, that in any of the arrangements illustrated, the spinneret or spinnerets may be positioned for either horizontal or vertical spinning.

Various changes and modifications may be made in carrying out the method describedherein without departing from the spirit and scope ofr the invention asw defined in theilaappended claims: I

I claim-z I V 1; Method comprising extruding viscose :into a groups ofspinneretspas:shown inmiFigured- As 5 an acid setting bath to -eifect decomposition of? thewviscose and regeneration of cellulose hydrate" byLthe' action of: the bath; withdrawing the :bath

containing dispersed: particulate impuritiesrxresuiting i'from decomposition of "the viscosefrom 10 the zone .of extrusion cf the viscose; propagating high frequency zsoundwavesdnthefouled bath to eifect rapid sedimentation ofiitheimpurities and clarifyftheabathiunder the-influence of the waves,=: and separating: theil'clarified"supernatant batha:

fronrtheisediment:th-iisprOdubed. U

2. Method comprising extruding viscose intost;

anuacidl s'etting:bath to eilect decomposition of the'lv-iscose and regeneration: oft-c'ellulos"e "hydrate bythe actioniof 'the batht witlidrawing: the-bathe containing dispersed particulate impurities resulting from decomposition of the viscose from the zone of extrusion of the viscose, propagating high frequency sound waves in the fouled bath to effect rapid sedimentation of the impurities and clarify the bath under the influence of the waves, separating the clarified supernatant bath from the sediment thus produced, conditioning the bath for re-use in the regeneration of cellulose hydrate from viscose, and returning the bath to the zone of extrusion of the viscose.

3. Method comprising continuously extruding viscose into an acid setting bath to effect decomposition of the viscose and regeneration of cellulose hydrate by the action of the bath, continuously withdrawing the bath containing dispersed particulate impurities resulting from decomposition of the viscose from the zone of extrusion of the viscose, continuously passing the fouled bath through a field of high frequency sound waves at a controlled rate to effect rapid sedimentation of the impurities in the field, continuously circulating the clarified bath to a reconditioning zone for reconditioning for ,re-use in the regeneration of cellulose hydrate from viscose, and continuously circulating the clarified reconditioned acid setting bath to the zone of extrusion of the viscose.

4. Method comprising continuously extruding viscose into an acid setting bath to effect decomposition of the viscose and regeneration of cellulose hydrate by the action of the bath, continuously withdrawing the bath containing dispersed particulate impurities resulting from decomposition of the viscose from the zone of extrusion of the viscose and circulating it to a reconditioning zone, and intermediate of the extrusion and reconditioning zones, subjecting the fouled bath to high frequency sound wave radiations to effect rapid sedimentation of the impurities and produce a clarified solution under the influence of the waves.

5. Apparatus for use in the manufacture of regenerated cellulose articles from viscose comprising a vessel, means for introducing an acid setting bath into the vessel, at one end thereof, means for withdrawing the bath at a controlled rate from the vessel, means for extruding the viscose into the bath, and means associated with the vessel for subjecting the bath, after contamination thereof with dispersed particulate impurities resulting from decomposition of the viscose, to high frequency sound wave radiations to effect sedimentation of the impurities and clarify the bath under the influence of such radiations.

6. Apparatus for use in the manufacture of regenerated cellulose articles from viscose comprisin in combination, a vessel, means for introducing an acid setting bath into the vessel, at one end thereof, means positioned in the vessel for extruding the viscose into the acid bath, means for: withdrawing the spent bath containing dispersed particulate impurities resulting from decomposition of the viscose from the vessel, at

theother end thereof, a second vessel, means for 10;

circulating the spent bath to the second vessel, and means associated with the second vessel for subjecting thespent bath to high frequency sound wave radiations in said vessel to effect sedimentation of the impurities and clarify the 15 bath.

7-; Apparatus for use in the manufacture of regenerated cellulose articles from viscose comprising, in combination, a vessel, means for con- 8 1, tinuously introducing'an acid setting bath into the vessel, at one end thereof, means positioned in the vessel for continuously extruding the viscose into the acid bath, a second vessel, means 5 for continuously withdrawing the spent bath containing dispersed particulate impurities resulting from decomposition of the viscose from the first vessel, and for circulating the spent bath to the second vessel at a controlled rate, means associated with the second vessel for continuously subjecting the bath contained therein to high frequency sound wave radiations to effect sedimentation of the impurities in said vessel and clarify the bath, and means for continuously withdrawing the clarified bath from the second vessel.

JOHN ALFRED CALHOUN.

No references cited. 

5. APPARATUS FOR USE IN THE MANUFACTURE OF REGENERATED CELLULOSE ARTICLES FROM VISCOSE COMPRISING A VESSEL, MEANS FOR INTRODUCING AN ACID SETTING BATH INTO THE VESSEL, AT ONE END THEREOF MEANS FOR WITHDRAWING THE BATH AT A CONTROLLED RATE FROM THE VESSEL, MEANS FOR EXTRUDING THE VISCOSE INTO THE BATH, AND MEANS ASSOCIATED WITH THE VESSEL FOR SUBJECTING THE BATH, AFTER CONTAMINATION THEREOF WITH DISPERSED PRTICULATE IMPURITIES RESULTING FROM DECOMPOSITION OF THE VISCOSE, TO HIGH FREQUENCY SOUND WAVE RADIATIONS TO EFFECT SEDIMENTATION OF THE IMPURITIES AND CLARIFY THE BATH UNDER THE INFLUENCE OF SUCH RADIATIONS. 